[wordup] Digitizing Books One Word at a Time

[Adam Shand]

This is amazing, what a cool use of all that "wasted" time! I wonder  
how many sites are actually getting their captcha's from recaptcha? :-)

Adam.

Source: http://recaptcha.net/learnmore.html
A CAPTCHA is a program that can tell whether its user is a human or a  
computer. You've probably seen them — colorful images with distorted  
text at the bottom of Web registration forms. CAPTCHAs are used by  
many websites to prevent abuse from "bots," or automated programs  
usually written to generate spam. No computer program can read  
distorted text as well as humans can, so bots cannot navigate sites  
protected by CAPTCHAs.

About 60 million CAPTCHAs are solved by humans around the world every  
day. In each case, roughly ten seconds of human time are being spent.  
Individually, that's not a lot of time, but in aggregate these little  
puzzles consume more than 150,000 hours of work each day. What if we  
could make positive use of this human effort? reCAPTCHA does exactly  
that by channeling the effort spent solving CAPTCHAs online into  
"reading" books.

To archive human knowledge and to make information more accessible to  
the world, multiple projects are currently digitizing physical books  
that were written before the computer age. The book pages are being  
photographically scanned, and then, to make them searchable,  
transformed into text using "Optical Character Recognition" (OCR).  
The transformation into text is useful because scanning a book  
produces images, which are difficult to store on small devices,  
expensive to download, and cannot be searched. The problem is that  
OCR is not perfect.


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reCAPTCHA improves the process of digitizing books by sending words  
that cannot be read by computers to the Web in the form of CAPTCHAs  
for humans to decipher. More specifically, each word that cannot be  
read correctly by OCR is placed on an image and used as a CAPTCHA.  
This is possible because most OCR programs alert you when a word  
cannot be read correctly.

But if a computer can't read such a CAPTCHA, how does the system know  
the correct answer to the puzzle? Here's how: Each new word that  
cannot be read correctly by OCR is given to a user in conjunction  
with another word for which the answer is already known. The user is  
then asked to read both words. If they solve the one for which the  
answer is known, the system assumes their answer is correct for the  
new one. The system then gives the new image to a number of other  
people to determine, with higher confidence, whether the original  
answer was correct.

Currently, we are helping to digitize books from the Internet Archive.